Some 150 million tons of hay are baled in the United States each year, yet hay losses are probably larger than those of any other crop. Dry matter losses in hay making can reportedly range from 10-71% due to the various physiological and mechanical processes that the crop undergoes from the time the plant is cut until the hay is safely stored. Microbial degradation leading to mold formation and heat generation is among the principal causes of field losses in hay making. Hay will spoil if baled at moistures much over 12% unless preservations are applied to prevent fungal spoilage. Microbial activity and chemical oxidation cause heating in hay containing more than 15% moisture. Heat generation in baled hay increases dry matter losses, reduces nutrient digestibility, particularly protein and causes discoloration. Spoilage also causes loss of palatability and production of toxins.
If the disadvantages of microbial degradation, particularly mold formation and heat generation, could be alleviated, baling hay at higher moisture levels could provide direct benefits to the grower. The field curing process could be shortened, thereby reducing the exposure of plant nutrients to the destructive actions of sun, rain, and microbes. Entire cuttings are frequently lost due to untimely rainfall, for example, and these losses could be curtailed by baling the hay sooner, at higher moisture levels. Without a hay preservative, hay dry enough to bale without spoiling is crisp, and the fragile plant parts that are the most nutritious crop components shatter easily and so are lost as chaff as the hay is tedded, raked and baled. Higher moisture content also increaes palatability and thus decreases waste after hay is harvested. Indirect losses associated with field drying could also be reduced by baling high-moisture hay. Tractor wheel damage to rejuvenating plant crowns can be reduced by minimizing the tedding and crimping manipulations that are typically used to foster field drying. In addition, the grower can irrigate and fertilize sooner, and thereby enhance the production of the next cutting. It is consequently desirable to devise treatments that permit the grower to bale hay at higher moisture levels, on the order of 12% to 30% moisture, without heating or molding.
It would also be desirable to devise treatments that permit storage without heating or molding of grains having moisture levels on the order of 13% to 28% moisture. For example, microbial degradation of milled grains that serve as poultry rations severely impacts the poultry industry. Poultry are particularly sensitive to mycotoxins. The poultry rations leave the mill at about 12% moisture content but are typically stored for several weeks in farm grain bins before being fed out to broilers, layers, and turkeys. Due to condensation during transport and storage, and also metabolic water production, the milled grains tend to spoil in the grain bins, and so the rations are routinely treated with mold inhibitors. Such preservation treatments cost the poultry farmer on the order of one dollar or more per ton of rations. Considering that some four billion broilers are raised annually in the U.S., each consuming an average eight pounds of rations, there is and has been a tremendous incentive to find more cost-effective preservative treatments for milled grains.
Many efforts have been made to provide compositions and methods for preserving high-moisture content crops such as hay and grain against the deleterious effects of microbial degradation. Propionic acid has been used with some success as a hay preservative. See, for example, Agron.J. 68:120-123, 1976; Ann.Appl.Biol. 88:65-73, 1978. Propionic acid has also been combined with a variety of adjuvants for reported synergistic effect. Indeed, many if not all of the current commercial hay preservative preparations rely upon propionic acid aas the sole or principal preservatively effective ingredient. Unfortunately, propionic acid is a volatile, pungent chemical that is highly corrosive to farm machinery.
Also of interest are references to the use of carbamate compounds, particularly sodium methyl dithiocarbamate, as antimicrobial agents. U.S. Pat. No. 2,792,327 discloses the application of sodium monomethyl dithiocarbamate to control fungus infestation of living vegetation. U.S. Pat No. 3,699,231 reports a synergistic mixture of sodium methyl dithiocarbamate and formaldehyde to inhibit the growth of sulfate reducing bacteria. U.S. Pat. No. 3,836,655 reports a synergistic mixture of sodium methyl dithiocarbamate and propionic acid for preserving moist grain during storage. See also: U.S. Pat. No. 2,614,957 (sodium dimethyl dithiocarbamate admixed with the sodium salt of 2-mercaptobenzothiazole); U.S. Pat. No. 2,614,959 (zinc dimethyl dithicarbamate admixed with the ferric salt of mercaptobenzothiazole); U.S. Pat. No. 2,776,922 (zinc salt of 2-mercaptobenzothiazole admixed with zinc salt of dimethyl dithio carbamic acidi); and U.S. Pat. No. 4,203,999 (antifuga bis (dithiocarbamate) salts).